1. Field of Invention
The present invention relates to a pivot assembly for sustaining magnetic heads, head suspensions and an actuator block pivotally parallel to magnetic disks in a hard disk drive.
2. Description of Related Art
A hard disk drive is formed, as shown in FIG. 3 in general, by disposing a plurality of magnetic disks D on a rotary axis C1 at a given spacing and arranging them in such a manner as these are driven to rotate in a unitary manner by a spindle motor not shown, while an actuator block (swing arm) 2 to support a plurality of head suspensions 1, on each tip end of which a magnetic head is mounted, being pivoted in multiple steps on a pivot assembly 3 having a pivotally axis C2 parallel with the rotary axis C1 and, by generating a voice coil motor not shown but disposed on a proximal end 2a side of the actuator block 2, the actuator block 2 is made to swing on the pivotally axis C2 to access the magnetic head to a desired position of the magnetic disk D.
Here, the above pivot assembly 3, as shown in FIG. 4, comprises a hollow shaft 4 disposed at a pivoting center (pivotally axis C2) of the actuator block 2 and a sleeve 7 which is coupled with the shaft 4 pivotally and provides its outer diameter surface as a peripheral face to couple the actuator block 2 through a pair of rolling bearings 5, 6. The pair of rolling bearings 5, 6 are positioned in an inner diameter 7a having a large diameter formed at both ends of the sleeve 7 and coupled in the respective positions to the sleeve 7. While, the sleeve 7 is fixed in its axial-directional position by making the one side (lower end side) rolling bearing 6 seated on a flange portion 4a to the shaft 4. Now, the shaft 4 is adapted to be fixed in its position by making use of an internal thread 4b to a housing (not shown) of the hard disk drive.
Now, the rolling bearings 5 and 6 have such constitution in general as a plurality of balls 13 are interposed between a raceway of an inner ring 11 and a raceway surface of an outer ring 12 and the balls are adapted to be distributed by same spacing between each other on the circumferential direction by a retainer (not shown), however, in terms of using the above rolling bearing for sustaining a consistent rotational load, in order to guarantee a stable rotating accuracy, on both sides within the spacing between the inner ring 11 and the outer ring 12 a sealing member 14 such as a shield plate and seal plate or a doubled seal formed by being doubled with seal plates (in figure, a shield plate is shown) is disposed in order to prevent a leakage of a lubricant toward outside the rolling bearing and/or in order to prevent contamination of a lubricant by foreign material from outside the rolling bearing.
However, according to the use of the rolling bearings 5, 6 with the sealing member 14, to form a circumferential groove 15 (the circumferential groove provided in an inner diameter surface of the outer ring 12) for coupling and holding a shield plate or seal plate on the inner diameter surface of the outer ring 12 or instead of the circumferential groove 15, a circumferential groove on the outer diameter surface(not shown) of the inner ring 11 requires machining process. Also, by the sealing member 14 such as the shield plate or the seal plate and disposing the sealing member 14 process on the circumferential groove 15, manufacturing cost is increased, causing an increase of the manufacturing cost of the pivot assembly for a hard disk drive.
The invention has been made to be improved of the above problem. The purpose thereof is to retaining sealing capability and achieving a cost reduction in general, by simplifying the sealing structure and reducing a number of the sealing member for the rolling bearing, thereby to provide a pivot assembly contributing to the cost reduction of the hard disk drive.
A pivot assembly for sustaining magnetic heads, head suspensions and an actuator block pivotally parallel to magnetic disks oscillates slowly. Hence the invention has been made in light of examining a sealing structure for retaining sufficient capability of preventing a leakage of lubricant and retaining sufficient capability of preventing a contamination of lubricant, characterized in that retaining required sealing capabilities, an annular shield plate is secured to the shaft, achieving pivot assembly manufacturing cost by reducing machining process and a number of sealing members.
That is, the constitutional feature of the present invention resides in that, in a pivot assembly which comprises a shaft disposed at the pivoting center of the actuator block to support the head suspensions to be provided with magnetic heads and a sleeve which is mounted pivotally on the shaft through a pair of rolling bearings and provides the outer diameter surface as a coupling surface for the actuator block, an open bearing as sealing member-less rolling bearing is used and the shaft to be used to secure an annular shield plate forming a tiny gap between both an outer ring end face and an inner ring end surface at each opening end of open bearing.
In the pivot assembly thus formed, since the shield plate seals an opening end of the open bearing by the function mentioned above, a circumferential groove 15 in the inner diameter surface of the outer ring 12, the mounting of the sealing member, such as shield plate or seal plate and the assembly process of the sealing member into the bearing, become unnecessary.
The invention still requires a sealing plate to every open bearing to prevent the leakage of lubricant toward outside the rolling bearing and/or to prevent contamination of a lubricant by foreign material from outside the rolling bearing, eliminating the circumferential groove and reducing the number of sealing member contribute to a cost reduction. A further embodiment characterized in that where the shaft has a flange portion to support one of the open bearing and a radially extending portion functions as the shield plate, having gaps between the outer ring end surface, thus reducing one more shield plate.